I. Field of the Invention
The present invention relates to a process for manufacturing seal members from a hard material wherein the sealing effect is due to the precise finish of the sealing members and not by the interposition of any seals of pliable material. These seal members may be utilized in faucets, industrial valves, and injection pumps for diesel engines.
II. Description of the Prior Art
Sealing disks manufactured from hard materials and utilized as fluid flow regulation and interruption devices in faucets and the like, are conventionally produced with oxides or sintered aluminum silicates ground to a roughness of about 0.2 to 0.4 microns. Because of these precise finishes, these disks cooperate to form seals suitable to regulate and interrupt fluid flow through the system. Moreover, due to the strength of the materials utilized, normally 23,000 N/mm.sup.2, these past known seal disks have an improved effective life and can resist foreign bodies, such as grains of sand, which may damage previous seal members. However, because of the precise finish of the working surfaces between the seal disks, these disks tend to adhere to one another which, without any lubricant, increases the friction between the disks. The normal coefficient of these past materials is in the nature of 0.12.
In order to provide efficient rotation of these seal disks in relation to each other and proper operation of the faucet, a thin layer of a silicon lubricant is provided between the disks. However, with time and repeated use of the faucet which causes the disks to rotate against each other, the silicon lubricant is gradually dispersed so that the friction between the disks increases to unacceptable levels. Eventually, the faucet will cease to operate.
Attempts have been made to produce these seal disks using wolfram carbide. However, manufacturing costs for this type of disk have proved to be prohibitive.
Further attempts have been made to produce the disks for faucets with a material composed of silicium carbide (SiC). The silicium carbide provides, in its known different crystallographic modifications, hardnesses between 28,000 N/mm.sup.2 and 35,000 N/mm.sup.2, which are much higher than the hardnesses of the materials presently used for this purpose, while providing frictional coefficients approaching 0.05. Moreover, this material has a reduced tendency for adhesion found in other smoothly finished surfaces thereby reducing the friction between the cooperating disks of the faucet. Despite these improvements in operation, the friction between the two disks made from silicium carbide has a tendency to increase beyond acceptable levels through extended usage.
Finally, the Applicant herein has constructed seal disks for faucets wherein the cooperating pair of disks have different frictional characteristics with at least one disk formed of silicium carbide. Although this process has provided a lasting reduction in the friction between the seal disks without the addition of a lubricant, the production and grinding of the disks formed from SiC require special plants and technologies. Thus, it was necessary to develop a process for manufacturing which could be widely and conveniently utilized yet would not be cost prohibitive.